The Pipe
Pipes come in all sizes and somewhat resemble a tobacco pipe. The difference usually being that the shape of a cannabis pipe is most often a cylinder.
Glass Pipes
Simple to artistic glass pipes are easy to clean and let you see the opaqueness of the smoke as the toke is drawn. Monitoring how much smoke was generated and how much you choose to inhale keeps you from coughing or ending your session early due to sore throat or lungs. Glass pipes are durable but not meant to be dropped or jostled around in a bag without padding.
Diverse Materials
Ceramic pipes are typically cheaper but tend to be painted as opposed to clear so it’s more difficult to see how much smoke you're getting from a toke.
Wooden pipes are often smaller and chosen for their portability and stealth with some offering flower storage.
Metal pipes are nearly indestructible, for outdoor activities or frequent transport, but get hot with lots of use and have the harshest smoking experience.
Popularity
Pipes are still as popular as joints as a way to consume cannabis. They are simple to use and can be easy to conceal. However, they can be smelly to transport unless kept in a carrying case.